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Astronomi

Rabu, 27 Maret 2013

Ellychnia corrusca

Ellychnia corrusca fireflies live in forested areas over
much of the eastern United States. Based on its physical structure and
certain DNA sequences, this firefly is thought to be closely related to Photinus fireflies, but exhibits some remarkable differences. E. corrusca is a daytime firefly and, unlike Photinus, the adults do not have light organs. Light organs are, however, present in the larvae.
This study was conducted to add to existing information on the life history and mating habits of E. corrusca.Overwintering Mortality and Population Dynamics
Adult E. corrusca overwinter in the crevices of oak and other
thick-barked trees. Their survival rate during the winter is high, close
to 100%. Of those that did not survive, some were found intact on
their backs in the snow, suggesting freezing as a cause of death.
Predation as an additional cause of death was indicated by the detection
of wing covers at the bases of the trees.E. corrusca fireflies become active in early March, as
witnessed by increased movement along the barks of trees, and mating
pairs were noted by April and May. Using mark-recapture methods in the
field, more than 800 adults were marked in the spring. After the spring
mating season, no adults were found by June and July. Adults appeared
again in August, congregating on their wintering trees, but of these
adults sighted in the fall, none were marked. The evidence suggests that
E. corrusca adults die after the spring mating, and that the fall beetles are newly-emerged from eggs laid in the spring.Feeding Behavior
In the spring, adult E. corrusca were seen actively feeding on
the nectar of Norway maple flowers and the sap of sugar maples. Many
were found drowned in the sap-collection buckets for maple sugaring.
Adults were also found at the bases of trees, apparently drinking from
moisture on the ground. Some researchers also observed these fireflies
feeding on asters in the fall, but none were seen to do so in this
study.Mating Behavior
Mating season for E. corrusca lasts about six weeks, with the
last sighting occurring on May 21. Mating occurs mostly on tree trunks,
and involves two stages. In the first stage, the male mounts the back
of the female, brushing his antennae across her thorax. This may
continue for 2 to 20 minutes.
In the second stage, the male swivels around, facing away from the
female. This stage can last many hours, and while joined, the male and
female may wander a considerable distance over the tree.
In the laboratory, males and females mated multiple times, as often
as 11 times, with an average of three matings per male and four per
female.

Discussion

This study revealed several interesting aspects of E. corrusca’s life history that differ from that of most other fireflies.
As adults, E. corrusca live approximately ten months of the
year — August through May. They spend the winter hibernating on the
barks of trees. Fat body reserves are higher in the fall and lower in
the spring, suggesting that fat is used as an energy source during the
winter. Although their winter survival rate is high, some will succumb
to freezing and predation. When attacked, they will reflex bleed like
other fireflies, and their bitter taste (personal observations by the
researchers) may deter predators.
These fireflies mate in the early spring on their overwintering trees
and die in the late spring/early summer. Adults that appear the next
fall are presumably the offspring of the adults that mated the previous
spring.
A daytime firefly, E. corrusca adults do not possess light
organs and do not communicate by flashing. The cause may be the low
nightly temperatures during the spring mating season, prohibiting their
nighttime flight and bioluminescent displays.
Despite these differences to other fireflies, E. corrusca’s reproductive anatomy and mating behavior suggest they are closely related to Photinus fireflies.